Shrink-wrap film heating apparatus

ABSTRACT

Apparatus for heating shrink-wrap film includes a heating space incorporating a heater element and a fan. A shrinkage chamber is formed by a pivotal hood disposed alongside the structure defining the heating space and pivotal movement of the hood effects control movement of flap valves in ducts leading to and from the shrinkage chamber so that when the chamber is open the flap valves are closed and vice versa.

United States Patenti Wieligmann July 4, 1972 [54] SHRINK-WRAP FILM HEATING [56] References Cited APPARATUS UNITED STATES PATENTS 72 l ntor: Fried h W' Ii nn W it k I I 'gg 3,399,506 9/1968 Howe .34/225 x 3,430,358 3/1969 Denker.... ..34/225 X [731 Asslgmi g g Laggenbeck/Westphaha, 3,586,516 6/1971 Terc ..34/22s x 122 Filed: 35612:,1971 I Primary Examiner-Carroll B. Donty, J rt {21] PP 108,477 Attorney--Mason,Mason&Albright [30] Foreign Application Priority Data [57] ABSTRACT Jan. 22, i970 Germany ..P 20 02 786.5 Apparatus for heating shrink-wrap film includes a heating space incorporating a heater element and a fun. A shrinkage [52] [1.8. II .34/225 Chamber is formed by a pivotal hood di alongside the is] I structure defining the heating space and pivotal movement of [58] held oibearch ..34/2l2,213,219,223522g the hood effects control movement of flap valves in ducts leading to and from the shrinkage chamber so that when the chamber is open the flap valves are closed and vice versa.

6 Claims, 1 Drawing Figure SHRINK-WRAP FILM HEATING APPARATUS I BACKGROUND OF THE INVENTION 1'. Field of the Invention The invention relates to heating apparatus for wrapping stacks of articles with shrink-wrap film.

2. Description of the Prior Art German utility model specification 1,958,765 shows a heater for shrink-wrap film in the form of a chamber to which warm air can be admitted and through which stacked goods (moulded bricks, for example) are moved on trolleys. Upon completion of the shrinkage process, thedoors of the shrinkage chamber are opened and the loaded trolleys are run out.

The disadvantage of this previously proposed heater is that the goods being packed must be moved by the conveyor mechanism out of the shrinkage chamber along with the softened film when the doors are opened at the expiration of the predetermined shrinkage time, since otherwise the film is overheated and accordingly burnt. This makes it necessary for the timing of the conveying mechanism to be governed by the shrinkage time. In most cases, however, the widely varying times taken to charge the conveyor with goods, to draw the film cover into position and to remove the goods once they have had their covers shrunken on, cannot be adapted to the shrinkage time. The conveyor taking goods through the heater must therefore be preceded and followed in each instance by another separately driven conveyor on which the goods are placed. The provision of several such conveyors, however, is complicated and uneconomic Another proposed shrink-wrap film heater has a shrinkage chamber to which hot air can be admitted and which is opened when stacked goods shrouded in film are inserted and is closed while hot air is being fed to the film, as well as a heater space housing an air heater and fan, which space can be connected to an air inlet duct and an air outlet duct serving the shrinkage chamber, and cut-off devices for the air inlet and outlet ducts, which close the connections between the heater space and the shrinkage chamber and open a duct for circulating the air within the heater space when the shrinkage chamber is open.

An object of the invention is to provide an improved shrinkwrap film heater so as to make the timing of the conveyor trolleys independent of the shrinkage time.

SUMMARY OF THE INVENTION According to the present invention there is provided a shrink-wrap film heating apparatus comprising a shrinkage chamber to which hot air can be admitted and which is opened when stacked goods loosely shrouded in film are inserted and is closed while hot air is being fed to the film, a heater space housing an air heater and fan, which space can communicate with an air inlet duct and an air outlet duct serving the shrinkage chamber, and cut-off devices for the air inlet and outlet ducts, which can close the connections between the heater space and the shrinkage chamber and open a duct for circulating the air within the heater space when the shrinkage chamber is open, the shrinkage chamber being formed by a hood which is fitted at one side of the heater space and can be pivoted upwardly to open the chamber. I

Further according to the present invention there is provided heating apparatus for shrinking on to at least one article a shrink-wrap film said apparatus comprising means defining an air heating space and incorporating therein a heating element and a fan, a hood pivoted to the air heating space means and defining a shrinkage chamber which can be opened for the insertion and removal of articles and closed when the shrinkage process is taking place, an air inlet duct providinG communication between the heating space and the shrinkage chamber, an air outlet duct providing communication between the shrinkage chamber and the heating space, flow-control means in the inlet and outlet ducts, and a by-pass duct enabling the hot air flow to by-pass the shrinkage chamber, when the shrinkage chamber is open, said by-pass duct being controlled by said flow-control means.

BRIEF DESCRIPTION OF THE DRAWINGS A sectional view of one embodiment of heating apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing.

The reference numeral 1 has been used to designate a casing comprising a top 2, an outer wall 3, and a bottom 4. The

two cross walls, which run in the direction of the plane of the drawing and cannot be seen therein, close the casing 1 on both sides.

A shrinkage hood 5, is hinged at 6 to the casing top 2. The hinge at 6 enables this hood to be pivoted upwards. A tension device (not shown) is attached to an eye 7 and serves to impart this upward pivotal motion to the hood 5.

Below the point of attachment of the hinge 6 is an intermediate wall 8, by which a shrinkage chamber proper 9, is separated from a heater space 10.

In the upper part of the intermediate 'wall 8, directly below the casing top 2, is a passage 11, through which the duct 12 is in communication with the duct 13.

The duct 12 forms part of the heater space 10 and is separated by a partition 15, from another duct 14.

A cut-off device in the form of a flap 16, in front of the passage 11, serves to open and close the ducts 13 and 14.

In the lower portion of the partition 15, but above the casing bottom 4, there is a hole 17, connected by an inlet 18, to a radial-flow fan 19, driven by a motor 20.

Inside the duct 12, above the radial fan 19, are electrical heating elements 21, which heat the air blown by the fan 19. It is also possible, of course, for other kinds of heating elements to be used, such as, for example, gas or oil burners.

The duct 13 is bounded by a part 5a of the casing top of the shrinkage hood 5 and by a grid or other metal sheet 22, fixed to the latter.

This sheet 22 contains slots 23,- the efi'ective size of opening of which can be varied by means of sliding shutters 24. This adjustment facilitates the distribution of the air in the shrinkage chamber 9.

The floor of the shrinkage chamber 9 is formed by a trolley 25, which runs on rollers 26 and 27, along rails 28 and 29, the dimensions of the trolley bottom or platform 30 being precisely the same as those of the bottom of the shrinkage chamber 9.

A number of such trolleys 25 is arranged in succession to form an endless belt, so that the trolleys 25 emerging from the shrinkage chamber 9 and forthwith. unloaded are brought back, for a further run through the shrinkage chamber 9, on to the rails 28 and 29 that constitute the top track, by means of a track (not shown in the drawing) situated below the rails 28 and 29.

Each trolley bottom 30 is inclined at an angle such that the goods 31, shrouded in the their shrink-film covers, slide on the trolley bottom 30 towards the outer side 5b of the shrinkage hood 5 and come up against a strut 32 or other stop.

The trolley bottom 30 is hollow, so that the heated air entering the shrinkage chamber 9 flows past the goods 31 and into the space 33 in the trolley bottom 30, through which it passes, emerging from an outlet 34 in the underside plate 3000f the trolley bottom 30, and is directed by trunking 35 fixed-to the plate.30a,to an admission aperture 36. Then the air passes through a passage 37 to the radial fan 19.

The admission aperture 36 is fitted with a cut-off member in the form of a flap 38. The operation of the two cut-offs 16 and 38 can be controlled either by the hood 5 or independently thereof, the effect being that during the shrinkage process, when the hood 5 is down, the two ducts 13 and 37 are opened and the duct 14 is closed at the air admission end, whereas, when the hood 5 is raised, the two ducts l3 and 37 are closed and the duct 14 is opened.

The mode of operation of the heating apparatus in accordance with the invention is as follows:

As soon as one of the trolleys 25 carrying the shrink-wrap covered goods 31 has been run into the shrinkage chamber 9, the hood 5 is lowered and the shrinkage process begins.

To that end, the radial-flow fan 19 blows air into the duct 12, where it is heated to the requisite shrinkage temperature by the heater elements 21. From there, the heated air flows through the passage 11 into the duct 13, passes through the slots 23 into the shrinkage chamber 9 and flows round the goods 31, so that the shrink-wrap film is raised to the shrinkage temperature.

The air is led away through the space 33 in the trolley bottom 30, which directs it through the outlet 34 into the trunking 35.

The air then flows through the fan inlet 36 and on through the passage 37, whence it is drawn by the fan for re-use.

During this shrinkage process, the flap l6 closes theduct l4 and opens the passage 1 l to the duct 13, the flap 38 in front of the admission aperture 36 remaining open. With the flaps in this position, a powerful air circulation is set up, starting from the heater space 10 and extending through the shrinkage chamber 9. a I

On completion of the predetermined shrinkage time, the hood 5 is pivoted upwardly and the packedgoods stand free, the shrink-wrap .film being then surrounded by ambient air so that it can cool and contract.

Simultaneously with the raising of the hood 5, the flap l6 closes the duct 13 and the flap 38 closes the inlet 36. In the drawing, the'flaps-l6 and 38 in this position are indicated by broken lines."

The air is now driven round a reduced (by-pass) circuit, past the electric heater elements 21 in the duct 12 and into the duct 14, whence it is led back to the fan 19.

The trolleys 25 having been indexed, the shrinkage process is repeated, the hood 5 being lowered over the goods 31 newly run into position, while the position of the flaps 16 and 38 is changed simultaneously to enable the air that has already been pre-heated in the by-pass circuit to pass from the heater space to the shrinkage chamber 9.

in the "shrink-wrap film heating apparatus hereinbefore.

described, the shrinkage hood can be pivoted so as to leave the packed goods free, thereby enabling the film to cool and contract, without the trolleys having to be moved at set intervals. Hot air is admitted to the shrinkage chamber only when the hood is down.

With the hood up, the air is heated within a short, isolated circuit. Thus, no hot air passes into the opened shrinkage chamber, as is the case with heaters hitherto proposed.

The timing of the conveying trolleys becomes independent of the shrinkage time. Only one conveying system is therefore required, this being controlled not by the shrinkage time, but by the loading, shrink-wrap film covering and/or unloading of the goods being packed.

The transference of goods to sundry means of conveyance is eliminated, which makes the process cheaper.

I claim:

1. Heating apparatus for shrinking on to at least one article a shrink-wrap film said apparatus comprising means defining an air heating space and incorporating therein a heating element and a fan,

a hood pivoted to theair heating space means and defining a shrinkage chamber which canbe opened for the insertion and removal of articles and closed when the shrinkage process is taking place,

an air inlet duct providing communication between the heating space and the shrinkage chamber,

an air outlet duct providing communication between the shrinkage chamber and the heating space,

flow-control means in the inlet and outlet ducts, and

a by-pass duct enabling the hot air flow to by-pass the shrinkage chamber, when the shrinkage chamber is open,

said by-pas duct being controlled by said flow-control means. 2. Apparatus according to claim 1, wherein said flow-control means comprise pivotal flap valves.

3. Apparatus accordin to claim 1 comprisin an arr inlet grid in the s rmkage chamber, an 

1. Heating apparatus for shrinking on to at least one article a shrink-wrap film said apparatus comprising means defining an air heating space and incorporating therein a heating element and a fan, a hood pivoTed to the air heating space means and defining a shrinkage chamber which can be opened for the insertion and removal of articles and closed when the shrinkage process is taking place, an air inlet duct providing communication between the heating space and the shrinkage chamber, an air outlet duct providing communication between the shrinkage chamber and the heating space, flow-control means in the inlet and outlet ducts, and a by-pass duct enabling the hot air flow to by-pass the shrinkage chamber, when the shrinkage chamber is open, said bypass duct being controlled by said flow-control means.
 2. Apparatus according to claim 1, wherein said flow-control means comprise pivotal flap valves.
 3. Apparatus according to claim 1 comprising an air inlet grid in the shrinkage chamber, and sliding shutter means for closing the openings of the grid.
 4. Apparatus according to claim 1 comprising trolleys for conveying the stacks of articles through the shrinkage chamber.
 5. Apparatus according to claim 4, wherein each said trOlley has a hollow platform serving as an air outlet duct from the shrinkage chamber.
 6. Apparatus according to claim 4, wherein each said trolley has a platform inclined to the horizontal and said platform has a member arranged to prevent articles from slipping on the platform. 